1. Field
This disclosure relates to automating the management of airspace. In particular, the present disclosure is concerned with detecting conflicts between aircraft passing through managed airspace, and to resolving the detected conflicts strategically.
2. Background
Air traffic management is responsible for the safe passage of aircraft through an airspace. The aircraft may be manned or unmanned. To do this, a centralised, ground-based air traffic management facility must communicate with aircraft flying through the airspace it manages. This two-way communication may be done in a number of ways, including by oral communication such as by radio or by data communication through a data link or the like.
The aircraft may determine their desired flight path through the airspace, for example using an airborne flight management system, and may then communicate this to air traffic management. In modern times, air traffic management uses sophisticated computer systems to check the submitted flight paths do not result in aircraft trajectories that give rise to conflicts. Conflicts between aircraft arise when their intended trajectories would result in a separation falling below the minimum specified. By trajectory, a four-dimensional description of the aircraft's path is meant such as a time-ordered sequence of aircraft states, including position and altitude. Maintaining safe separations is a particularly demanding task, particularly in congested airspace such as around airports where flight paths tend to converge.
In addition to detecting conflicts, air traffic management must have the means to be able to resolve the conflicts and to communicate the necessary changes in trajectories to the conflicted aircraft.
To date, most efforts aimed at air traffic management's ability to detect and resolve air traffic conflicts have focused on crossing traffic patterns and have not dealt with the more challenging problem of converging traffic. This arises, for example, in arrivals management at TRACON (terminal radar control) facilities, where aircraft arrive from many directions and must be sequenced for approach and landing at an airport. The efforts directed to converging traffic consider maximizing the throughput of traffic on an airspace resource such as a sector or a runway as the main or sole objective when solving air traffic conflicts. Existing solutions also focus on planning the arrival sequence first before detecting and resolving conflicts. The method then proceeds by extrapolating that sequence backwards to the earlier waypoints. However, such an approach only serves to propagate the delay backwards to all other aircraft.
Previous attempts at detecting and resolving conflicts suffer other problems. For example, previous attempts have analysed conflicts in isolation from each other, typically as isolated events between pairs of aircraft. The detected conflicts are resolved in a sequential manner without any consideration of the possibility of a “domino effect” feeding back delays.
Recent advances in predicting aircraft trajectories accurately are of benefit to air traffic management. In particular, work on expressing aircraft intent using formal languages provides a common platform for the exchange of flight information and allows different interested parties to perform trajectory calculations. For example, this aids the communication of planned trajectories between aircraft and air traffic management.
EP patent application 07380259.7, published as EP-A-2,040,137, also in the name of The Boeing Company, describes the concept of aircraft intent in more detail, and the disclosure of this application is incorporated herein in its entirety by reference. In essence, aircraft intent is an expression of the intent of how the aircraft is to be flown. The aircraft intent is expressed using a set of parameters presented so as to allow equations of motion governing the aircraft's flight to be solved. The theory of formal languages may be used to implement this formulation. An aircraft intent description language provides the set of instructions and the rules that govern the allowable combinations that express the aircraft intent, and so allow a prediction of the aircraft trajectory.
Flight intent may be provided as an input to an intent generation infrastructure. The intent generation infrastructure may be airborne on an aircraft or it may be land-based such as an air traffic management facility. The intent generation infrastructure determines aircraft intent using the unambiguous instructions provided by the flight intent and other inputs to ensure a set of instructions is provided that will allow an unambiguous trajectory to be calculated. Other inputs may include preferred operational strategies such as preferences with respect to loads (both payload and fuel), how to react to meteorological conditions, preferences for minimising time of flight or cost of flight, maintenance costs, and environmental impact. In addition, other inputs may include constraints on use of airspace to be traversed.
The aircraft intent output by the intent generation infrastructure may be used as an input to a trajectory computation infrastructure. The trajectory computation infrastructure may be either located with or away from the intent generation infrastructure. The trajectory computation infrastructure may comprise a trajectory engine that calculates an unambiguous trajectory using the aircraft intent and other inputs that are required to solve the equations of motion of the aircraft. The other inputs may include data provided by an aircraft performance model and an Earth model. The aircraft performance model provides the values of the aircraft performance aspects required by the trajectory engine to integrate the equations of motion. The Earth model provides information relating to environmental conditions, such as the state of the atmosphere, weather conditions, gravity and magnetic variation.